If this were the software business, no one would bat an eye. But why are carmakers, notoriously secretive and possessive about their intellectual property, suddenly so eager to share?

Some analysts smell blood in the water, and see it as a sign of desperation, reflecting the tiny sales of electric and fuel-cell vehicles thus far. Under a slightly more optimistic reading, the moves are a pragmatic recognition that alternative-fuel car business needs to grow like gangbusters before any one company makes them profitable. Tesla, for example, can only be a true success if the electric car industry balloons into the millions of sales per year. So CEO Elon Musk is giving away his patents with the confidence that, when there is a critical mass, he will triumph by making the coolest and most desirable cars.